HTML API: Respect tag_name query arg in HTML_Processor::next_tag()

Previously the HTML Processor was ignoring the `tag_name` argument in
the `next_tag()` query if it existed. This was wrong adn would lead to
calling code finding the very next tag, regardless of tag name, instead
of the requested taag.

This patch adds the tag name detection code into `next_tag()` to fix
the bug and ensure that `next_tag()` always returns only when finding
a tag of the given name.

Developed in #6980
Discussed in https://core.trac.wordpress.org/ticket/61581

Follow-up to [56274].

Fixes #61581.


git-svn-id: https://develop.svn.wordpress.org/trunk@58681 602fd350-edb4-49c9-b593-d223f7449a82

Author: dmsnell

src/wp-includes/html-api/class-wp-html-processor.php

@@ -466,6 +466,10 @@ public function next_tag( $query = null ) {
 					continue;
 				}
 
+				if ( isset( $query['tag_name'] ) && $query['tag_name'] !== $this->get_token_name() ) {
+					continue;
+				}
+
 				if ( isset( $needs_class ) && ! $this->has_class( $needs_class ) ) {
 					continue;
 				}